Have a spray tool for blending in

As the title suggests, the spray tool would help ALOT in blending in colors faster instead of using the old-way here (low opacity or changing color spectrum slowly) which takes hellalot of time.But i don't mean the usual spray tool that has full opacity and just fills in a certain area slowly with colors, that's actually not a spray tool.The one i'm mentioning, has: low opacity ranging from 10% to 20% in the middle circle radius then 30% to 45% at the middle(basically like a real spray can)